Various devices have keyboards for example for pocket calculators, elevator control, traveling crane control etc. to enter information. It often is a problem that a great number of keys are required for entering of the necessary information. The presence of a great number of keys poses a problem, because it is difficult to select the correct key when there is great number of keys to select from. From a purely physical aspect, this also implies that it takes a longer time to move the fingers of the hand between different keys when a great number of keys is provided, i.e. the distance on the whole of the keyboard relative to the location of individual keys is longer.
For certain types of pocket calculators the above problem of many keys has been somewhat reduced by the introduction of some function keys, for example two keys, each of which has been allotted three functions. The more function keys are introduced, however, the greater is the risk of making errors.
A key can be allotted several functions in different ways. By means of a function key, the function content of a greater number of keys in the board can be changed.
It further is possible to change the function content for the remaining keys as long as a certain key is held depressed, for example the key for capital letters in a typewriter.
By depressing harder a certain key--for example a repetition key--the key function is repeated, as for example in an electric typewriter by depressing the key for text underlining.
In certain control connections it also is known by repeated depressions to bring about a change in a control magnitude, which change is proportional to the number of depressions.
The invention:
Briefly, each individual key is given several functions by arranging different circuit connections, corresponding to said functions, consecutively in time slots, or time reference frames, or time intervals. By a first step, for example the depression of a key, a time course is started from a fixed reference connection, and by further steps with the same or another key, circuit connections corresponding to the length the time course is maintained, that is, the key is actuated which in its turn corresponds to certain functions.
The system has the advantage that the number of keys required can be reduced substantially. Theoretically, a keyboard of any great size can be replaced by one single key, i.e. the function content of the key can be changed an unlimited number of times. In practice, however, the function content of a key is limited by the time of waiting for the desired function and circuit connection, respectively, and by the reaction time, i.e. the time required for safely releasing the key at the moment intended.
The exchange of function and circuit connection, respectively, can be displayed in a simple manner on a screen or by other optical and/or acoustical signal means.
The key functions can be exchanged more rapidly and safely than otherwise possible.